This application claims the benefit of Korean Application No. 2002-3386, filed Jan. 21, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates in general to plasma display apparatuses, and more particularly, to a plasma display apparatus having an over-current protection circuit that protects a switching device from an over-current generated during an abnormal driving of a driving circuit of a discharge sustaining electrode and a method of protecting over-current thereof.
2. Description of the Related Art
A plasma display panel (PDP) is a display apparatus using a discharge of gas. The PDP is generally classified into a direct current (DC) type that applies a facing discharge, and an alternating current (AC) type that applies a surface discharge, depending upon its driving type. The AC type PDP has attracted more attention because it has a lower power consumption and a longer lifetime in comparison with the DC type.
The PDP using the AC driving type applies an alternating current (AC) voltage between electrodes insulated with a dielectric layer, and performs a discharge every half-cycle of the AC voltage, which is used to display a picture mainly in a sub-field method. In the sub-field method, since the power consumption used for a charge and the discharge of the PDP panel during the sustain of the discharge is very large, a circuit is used to collect reactive power in a driving device of the PDP.
As illustrated in FIG. 2, a circuit to drive the discharge sustaining electrode generally includes a unit driving cell of a discharge sustaining electrode connected to a Y-electrode (hereinafter referred to as xe2x80x98Y-electrode unit driving cellxe2x80x99) and a unit driving cell of a common electrode connected in common to a plurality of X-electrodes (hereinafter referred to as xe2x80x98X-electrode unit driving cellxe2x80x99). The Y-electrode and the X-electrode perform a surface discharge with supplied sustain pulses generated in the X-electrode unit driving cell and the Y-electrode unit driving cell as sustaining electrode pairs. By this, brightness of the picture displayed on a screen is sustained. Here, a panel capacitor 41 indicates equivalently electrostatic capacity formed between the Y-electrode and the X-electrode in the panel.
Referring to FIG. 2, the Y-electrode unit driving cell includes a capacitor 43a to collect energy, first and third switches 35a, 37a connected in parallel with the energy collecting capacitor 43a, second and fourth switches 31a, 33a connected in series between a voltage supply source Vcc1 and a ground, and a coil 39a connected between a first node n1 and a second node n2. The X-electrode unit driving cell is positioned symmetrically relative to the Y-electrode unit driving cell through the panel capacitor 41.
To the branch point of the first node n1 and the second switch 31a are connected a reset resistance 45, a reset capacitor 47 and a reset switch 48 to reset a voltage of the panel capacitor 41. If the reset switch 48 is turned on, the voltages charged in the panel capacitor 41, the X-electrode unit driving cell, and the Y-electrode unit driving cell become uniform.
An operation of the discharge sustaining electrode driving circuit will be described below with reference to FIGS. 3A to 3E. The second switch 31a and a switch 49 to connect to the panel capacitor 41 (hereinafter, xe2x80x9cpanel capacitor connecting switchxe2x80x9d) are turned on during the reset, and the electric current then flows. If the panel capacitor connecting switch 49 is turned off during the flow of the electric current, the reset switch 48 is turned on. Thus, a bypass current is formed by the reset capacitor 47 and the reset switch 48. At this time, the electric current flowing in the panel capacitor 41 constitutes a reset pulse.
If the panel capacitor connecting switch 49 and the third switch 37a are turned on after the circuit is in the reset state and the current charged in the panel capacitor 41 is discharged, electric charge is transmitted to the energy collecting capacitor 43a and charging is performed. The first switch 35a and the panel capacitor connecting switch 49 are turned on during a voltage rising time t0 of the discharge sustaining pulse. An electric current due to the energy charged in the energy collecting capacitor 43a is transmitted to the panel capacitor 41, through the first switch 35a, the coil 39a and the panel capacitor connecting switch 49. On an end of the voltage rising time t0 of the discharge sustaining pulse, the second switch 31a and the panel capacitor connecting switch 49 are turned on, thereby allowing the discharge sustaining pulse to remain in a xe2x80x9chighxe2x80x9d state t1. On an end terminal point of the discharge sustaining pulse in the t1, the third switch 37a and the panel capacitor connecting switch 49 are turned on, the voltage of the discharge sustaining pulse reduces to a xe2x80x9clowxe2x80x9d state. The electric current due to the energy charged in the panel capacitor 41 is stored in the energy collecting capacitor 43a through the panel capacitor connecting switch 49 and the third switch 37a, and the discharge sustaining pulse is in the xe2x80x9csuspensionxe2x80x9d state. On an end point of a falling time t2 of the discharge sustaining pulse, the fourth switch 33a and the panel capacitor connecting switch 49 are turned on and the panel capacitor 41 is completely discharged, so the discharge sustaining pulse remains in the xe2x80x9clowxe2x80x9d state t3. The discharge is sustained through a repetition of the above-described processes.
If a sub-field ends, each switch 31a, 33a, 35a, 37a, 48, 49 is turned on or off so as to return back to the xe2x80x9cresetxe2x80x9d state to maintain the discharge sustaining pulse, and the discharge process is progressed, thereby allowing a plasma display panel to emit light. Also, like the Y-electrode unit driving cell, the X-electrode unit driving cell operates alternately with the Y-electrode unit driving cell through the above-described processes.
However, if any of the switches 31a, 33a, 35a, 37a, 48, 49 are abnormally turned on at the same time during the process of applying an on/off control signal to each of the switches 31a, 33a, 35a, 37a, 48, 49 while a conventional discharge sustaining electrode driving circuit has been driven, over-current flows into the switches 31a, 33a, 35a, 37a, 48, 49 by which they may be damaged.
The present invention has been made keeping in mind the above-described and other shortcomings, and an object of the present invention is to provide a plasma display apparatus having an over-current protection circuit that protects a switching device from the over-current generated during an abnormal driving of the driving circuit of discharge sustaining electrode.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
This and other objects of the present invention may be achieved by providing a plasma display panel apparatus according to an embodiment of the invention that includes a pair of discharge sustaining electrodes, a panel capacitor to supply charged voltage alternately to each electrode of the pair of discharge sustaining electrodes, at least one discharge switching device to perform a discharge, the switching device being turned on when the panel capacitor is discharged to thereby pass through discharged current of the panel capacitor, a current sensing part to sense the current passing through the discharge switching device, and an over-current controlling part to turn off the discharge switching device when the current sensed in the current sensing part is at or higher than a predetermined reference value.
According to an aspect of the invention, the current sensing part comprises a current sensing resistance connected in series to the discharge switching device, and the over-current controlling part comprises a comparator to compare the sensed voltage detected in the current sensing resistance with a predetermined internal reference value and to output a break signal, and switching device to break the current to control the discharge switching device to be turned on or off according to a xe2x80x9chighxe2x80x9d or xe2x80x9clowxe2x80x9d signal of the break signal.
According to another aspect of the invention, the over-current controlling part further includes a direct current (DC) converting part positioned between the current sensing resistance and the comparator.
According to a further aspect of the invention, the over-current controlling part further includes an OR gate disposed between the comparator and the break switching device.
According to yet another aspect of the invention, the discharge switching device comprises a field effect transistor.
According to a still further aspect of the invention, the over-current controlling part further includes a microcomputer to turn off the discharge switching device when the sensed current of the current sensing part is at or higher than the predetermined value.
According to another embodiment of the invention, a method of protecting over-current of a plasma display panel apparatus that includes a pair of discharge sustaining electrodes, a panel capacitor to alternately supply a charged voltage to each electrode of the pair of the discharge sustaining electrodes, and a plurality of switching devices to control the charged voltage to be alternately supplied from the panel capacitor to each electrode of the pair of discharge sustaining electrodes, the method comprising sensing current passing through the discharge switching device, and turning off the discharge switching device when the sensed current is at or higher than a predetermined reference value.
According to an additional aspect of the invention, the turning off the discharge switching device comprises converting the voltage according to the sensed current into direct current voltage, and turning off the discharge switching device where the converted direct current voltage is at or higher than a predetermined reference value.